The lung Is a unique epithelial surface at which inhaled particles, be they inert, bacteria or viral, are trapped in very close proximity to the bloodstream and in a filigree of epithelial surfaces. This presents unique spatial challenges for the T cells of the immune system to properly survey these antigens. Like many epithelial tissues, a selection of Immune macrophage and dendritic cells are poised within and beneath the surface to engulf and either neutralize, or to induce a more profound response to the Insult. During inflammatory insults including those of allergic but also bacterial or viral insults, the lung microenvironment physically changes. This new Project 2 will use live-imaging of viable lung and airways to determine how antigens traffic Into the lung and subsequently activate T cells, focusing the majority of effort upon a mouse model of asthma. The primary Issue being addressed is how inflammatory environments create a feedback loop that promotes accelerated immune responses and thus an enhanced inflammatory environment. We hypothesize that inflammation in the lung airway and aveolae creates a hyperreactive milieu for T lymphocyte priming. This milieu in turn is highly facilltative for synaptic interactions and thus increased production of lung remodeling factors Including cytokines. We propose that there are three distinct components of this. First, that there is a shift in the numbers, localization, antigen uptake and trafficking features between tolerizing phagocytic macrophages and highly immunogenic dendritic cells. The features of inflammatory antigens as well as the features of a remodeled milieu are both proposed to be directly responsible for the shift in the nature of APC which interact with T cells. Second, a shift In local polyclonal and antigen-specific regulatory T cells,modulated in part by the changes in APC population, subsequently modulates the activation of T cells. Finally, that T cells and their APC are modulated by airway remodeling and inflammation induced by agents such as Mycoplasma pulmonis or mast cell depletion. Thus, inflammation creates a fertile stimulatory ground for responses to inhaled antigens.